Which of the following concepts explains why an increase in the money supply results in a decrease in interest rates?

The real price level refers to the value of goods and services adjusted for inflation. While changes in the money supply can indirectly affect price levels, the real price level itself does not directly explain the mechanism through which interest rates decline. Thus, it is not a primary factor in the context of this question.

Income stabilization refers to measures aimed at maintaining consistent income levels across an economy. While a higher money supply can contribute to economic growth and stability, it does not directly address the causal link between increased money supply and decreased interest rates, thus rendering it irrelevant in this context.

Liquidity preference theory highlights how individuals prefer to hold cash, and when the money supply increases, the excess liquidity leads to lower interest rates as people seek to invest that surplus money. This direct relationship effectively explains why an increase in the money supply results in decreased interest rates.